Studies on maturity of sugar peas for canning in relation to their physical and chemical properties

Abstract

1. To compare the physical and chemical chan-ges occurring in maturing stage in the European sweet varities of sugar peas with those in the varie-ties which usually grown in Japan for canning and table use, some experiments were carried out in 1956 and 1957.
2. In the first year, Alaska, GW, and Oracle (sweet variety) were harvested four times at three day intervals from the 19 th to the 28 th day after flowering and were analyzed, It was found that Oracle variety was low in specific gravity, and conta-ined a small amount of alcohol insoluble residue which increased very slowly with ripening, as com-pared with the other two varieties. In Oracle va-riety sugar and soluble nitrogen contents were high, while starch and insoluble nitrogen contents were low regardless of the time harvested.
3. In the second year, Alaska, Usui and two sweet varieties, Provost and Oracle, were harvested from the 22nd to the 37th day after flowering. The results obtained in this year were similar to those of the first year. In grading by brine, it was found that in every harvest most of the peas of Provost and Oracle were in ‘Fancy’ class, while those of Alaska and Usui were in ‘Standard’ or ‘Second’ class. The peas of Alaska or Usui va-riety in ‘Fancy’ class, even if obtaind, were very immature and not available for processing.
4. As it was found that the stages of maturity proper to canning were very long in Provost and Oracle variety, it was possible to obtain the peas of high canning quality in large percentage even if they were harvested only one or two times. On the contrary, Alaska and Usui must be harvested many times because their proper stages of maturity were limited.
5. The canned products of Provost and Oracle variety were of excellent quality on account of their good flavor and clarity of liquid as compared with Alaska and Usui. In canned peas, even of the same class, the solid (drained) weight increased as the peas were harvested late because of increase in starch contents. In this case the Brix degree of liquid in cans increased according to maturity pro-bably because of absorption of water by starch par-ticles during sterilization.